A stratified air scavenged (SAS) two-cycle engine produces fewer emissions than a comparable displacement non-SAS two-cycle engine. As such, a SAS two-cycle engine can be very beneficial.
In general, a two-cycle engine directs a fuel mixture from a crank area of the engine to a cylinder block combustion chamber via at least one scavenging channel. The piston itself is used to control the flow of the fuel mixture via cyclic blocking/revealing of at least one scavenging port in a cylinder wall. However, the provision of the fuel mixture occurs as combustion gases are being ported from the engine. Within the SAS configuration, fresh air is utilized in order to minimize or prevent non-combusted fuel mixture from being outwardly ported from the engine along with the combustion gases. The piston itself is again used to control flow of the fresh air via cyclic blocking/revealing of at least one air port in the cylinder wall.
Typically, the cylinder block of an SAS engine tends to be long due to the space required for the air port(s) and associated fresh air passageway(s). In one example, the additional length is 8 mm, however, different additional length amounts are contemplated.